Corporatization of spam

Has anyone else noticed how spammers are now “corporatized”?

I have observed that 95% of my spam comes during normal (Eastern time – Central Time) business hours and little or none on weekends (if you don’t count lonely Russian girls and Nigerian scams).

It seems to me the most prolific spammers are regular nine-to-fivers, which implies corporate organization. The overwhelming concentration of sex spams is also an interesting twist that deserves some analysis.

Finally, is there any idea of the number of professional spamming sources? Once, a few years ago an urban myth was that there were two or three that were responsible; perhaps they’re organized.